Heating platen press

ABSTRACT

Heatable single or multilevel platen press for the manufacture of wood composition panels or the like, includes a stationary base structure and a hydraulically displaceable structure, each of the structures being composed of a plurality of individual bridge members and rib members interconnecting the bridge members and forming conjointly therewith a grid extending over the entire width of the press; press platens loosely mounted on the grid at the workpiece-side thereof, the rib members having fluid circulation passages for equalizing longitudinal thermal tensions, and the bridge members having fluid circulation passages for equalizing transverse thermal tensions.

United States Patent us; 3,685,932 Pfeiffer [451 Aug. 22, 1972 [54]HEATING PLATEN PRESS FOREIGN PATENTS OR APPLICATIONS Inventor: i iPfeiffer, Eppingen, Baden, 714,544 9/1954 Great Britain ..18/17 FGermany 1,048,767 11/1966 Great Britain ..18/17 H 1,033,223 7/1958Germany ..l8/17 H [73] Asslgneez J. Dieffenbacker GmbH Maschinenfabrik,Eppingen, Baden, Germany Filed: Aug. 27, 1970 Appl. No.: 67,412

Foreign Application Priority Data Aug. 27, 1969 Germany ..P 19 43 560.0

US. Cl. ..425/109, 425/339, 425/ 143, 144/281 Int. Cl ..B30b 7/02, B29j5/00 Field ofSearch ..18/16 P, 17 P, 17H

References Cited UNITED STATES PATENTS l-luetter 18/17 H X Siempelkamp..18/17 P Norton ..l8/l7 H X Hedin ..18/17HX Siempelkamp ..18/17 H X VanElten ..18/16 P X Primary Examiner-J. Howard Flint, Jr. Attorney-Curt M.Avery, Arthur E. Wilfond, Herbert L. Lerner and Daniel J. Tick [57]ABSTRACT l-leatable single or multilevel platen press for themanufacture of wood composition panels or the like,

includes a stationary base structure and a hydraulically displaceablestructure, each of the structures being composed of a plurality ofindividual bridge members and rib members interconnecting the bridgemembers and forming conjointly therewith a grid extending'over theentire width of the press; press platens loosely mounted on the grid atthe workpieceside thereof, the rib members having fluid circulationpassages for equalizing longitudinal thermal tensions, and the bridgemembers having fluid circulation passages for equalizing transversethermal tensions.

15 Claims, 7 Drawing Figures PATENTEUA G I972 3.685.932

sum 2 or 7 PATENTEDAuc22 I972 SHEET R [If 7 PATENTED 1:22 1912 SHEET 60F 7 HEATING PLATEN PRESS The invention relates to a heating platen forthe.

production of wood composition panels, such as chip or fiber boards andthe like, and more particularly to a heating platen press constructed asa single or multilevel press, having a stationary table and adisplaceable ram. Presses of this general type may be assembled ofprefabricated parts formed of a plurality of individual crossbeams orstruts, the individual crossbeams being subjected to the action of oneor more circulatory loops.

The most pressing problem in heating platen presses employed forproducing wood composition panels such as chip and fiber boards and thelike is to maintain the press surfaces formed by the press platen inplanar form as the pressure and heat are transferred to the materialbeing compressed, so that the compressed panel or board can emerge fromthe press with the least possible deviation from the nominal or datumthickness thereof.

The more the thickness of the completely pressed chipboard, fiberboardor the like corresponds to the nominal or datum value over the entiresurface area thereof, the more one can refer to the heating platen pressas being able to effect a plane-parallel pressure transfer.

The heretofore known platen presses of this general type are unable toattain this goal completely. The reason therefor is that the large-areawood composition panels are deformed as to their relatively slightthickness, due to the effect of the relatively high compression andtemperature, and lose the planar shape of the surface thereof which isimparted thereto during manufacture. This loss of planarity is sought tobe compensated by the crossbeams which are located between thepress-cylinder piston assemblies or the counter support, on the onehand, and the heating platen, on the other hand, which are also referredto as table and ram.

It has been found heretofore that, in order to attain plane-parallelismfor the press surfaces when compressive force is being transmittedwithout heat transfer, it is sufficient to provide the crossbeam partsengaged in the transmission of the compressive force with adequatelylarge dimensions. However, this constructive feature is inadequate ifthere is a transfer of heat up to 300 C together with transmission ofthe high compressive force even when the crossbeams are greatlyoverdimensioned.

In the known heating platen presses, the deformations in table and ramcaused by thermal stresses are sought to be prevented by providing incompensation of the one-sided heat flow of the heatedpress plates ontable and ram, a counter-heating on the opposite side thereof. Thiscounter-heating system is connectible to the circulatory loop on thepress platen or may constitute an individual circulatory loop. Adetrimental effeet is produced by stresses that occur during the heatingeffected between the heated and the unheated portions of table and ram,and thereby, deformations which are produced have a negative effect alsoupon the planar faces of the press platens. Stresses deriving from bothcirculatory heating loops produce deformations in the length and in thewidth which cannot be entirely eliminated even through a controlled heatsupply. Thus, the known heating platen presses do not offer asatisfactory solution despite their high costs of construction.

It is accordingly an object of my invention to provide heating platenpress especially formed with crossbeams, which, in connection with aplanned heating and cooling program, affords a trouble-freeplaneparallel pressure transmission to the material being compressed.

It is another object of my invention to provide heating platen presswith crossbeams of considerably simplified construction and to reducethereby the costs connected with the manufacture of the heating platenpress.

In heating platen presses having several circulatory heating loops whichare independent of each other, there is always a possibility that one ofthe heating loops will cease to function and that deformations caused bythermal stresses will occur in the table and ram, which can result indamage to individual components. It is therefore a further object of theinvention to provide heating platen press with safety means forpreventing such damage.

With the foregoing and other objects in view, I provide in accordancewith my invention, heatable single or multilevel platen press for themanufacture of wood composition panels or the like, comprising astationary base structure and a hydraulically displaceable structure,each of the structures being composed of a plurality of individualbridge members and rib members interconnecting the bridge members andforming conjointly therewith a grid extending over the entire width ofthe press; press platens loosely mounted on the grid at theworkpiece-side thereof, the rib members having fluid circulationpassages for equalizing longitudinal thermal tensions, and the bridgemembers having fluid circulation passages for equalizing transversethermal tensions.

With a proper selection of heating and cooling temperatures, thestructural features of the invention not only assure the balancing orcompensation of heat stresses within the table and ram, but in additionprovide a heat thrust in longitudinal direction of the heating platenpress above the neutral axis, as a counterforceto the heat thrustemanating from the heated press platen which acts below the neutral axisand would otherwise cause deformation in longitudinal direction.

The heat thrust in longitudinal direction of the heating platen pressmay be intentionally controlled when the ribs are divided in two and areformed of counterheating ribs and operational heating ribs which can besupplied with heat separately and differentially. Heat stresses in thetable and ram, which deform the planar surfaces of the press platen, canalso result from the fact that during the compression process, heatenergy will be removed too rapidly and in too large a quantity from thepress platen. In order that enough heat energy will be available in thetable and ram, in accordance with another feature of my invention, Iprovide the press platen, the bridge members and the rib members with aplurality of bores located in rows disposed one above the other in aplane.

To avoid damage to the press when a circulatory heating loop fails, Iprovide heating platen press, in accordance with a further feature of myinvention, with a safety loop wherein the bores of the press platen, thebores of the bridge members adjacent the press platen below the neutralaxis, and the bores of the counter- ,minimum deformation and consequentdeformation in the width of the ram and table..Secondly, due to thesmall amount of the counter-heating with respect to the total heatvolume, the temperature of thepress platen, the bridge members, as wellas the rib members, will decrease uniformly if the operational heatingfails, so that in this respect too, the necessary reliability is assuredfor the press.

In accordance with anadded feature of the invention, I provide heatingplaten press with a safety loop formed of a combination of thecirculatory loops for the operational heating and the counter-heatinginto one loop, only the bores in the bridge members adjacent the pressplaten being provided with an individual heating and cooling circulatoryloop with accurate control. In many publications dealing with theproduction of wood composition panels such as chip and fiber boardsdemand is made on the heating platen presses that the compressionprocess should start with press platens bent convexly about thelongitudinal center line, those press, platens first attaining theirplanar surfaces during the compression or pressing period. This isintendedprimarily so'that the steam cushion being formed can escapesatisfactorily as it, too, may be responsible for a negative productiontolerance when there is localizedinclusion. To meet this demand, inaccordance with an additional feature of my invention, small heatingplates mounted on the longitudinal center line of the press platen.

The bores of the small heating plates are connectible to the circulatoryloop of the operational heating system or may have their owncirculatoryloop. In both cases, the press platen'receives a greater supply of heatenergy around the longitudinal center line, and a convex deformation ofthe press platenis a result thereof. This desired deformation of thepress platen can be further facilitated if the bridge members also havehigher temperatures in the center and are convexly deformed in directiontowards the press platen.

I provide a further feature according to the invention toward this end,by disposing the bores of the bridge I that, accordingto the invention,the bridge members The realization of my'objective is aided by the factare shaped in accordance with the courseor direction of the stress by,the bending moment. The inventive I structural feature for-realizingthis solution provides for counter-heating system. This too can thenhelp also to supply the press platen with more heat about thelongitudinal centerline.

The advantages obtained by the invention are especially that through thenovel construction of the individual crossbeams, there is provided anopportunity for a planned and sensitive, thermodynamic control which canresult primarily in a trouble-free planar surface but which can alsoprovide a convex bendingthrough of the press platen in due time.

Another great advantage deriving from my invention is that the press isconstructed according to the static data or conditions by the maximalcompressive force and that no overdimensioning of the components whichtransmit the compressive force is required since the thermalstressforces are-small, if they exist at all, and can be countered at thedamaged locations quickly, for example, by distributing the heating orthe cooling action over several controllable circulatory loops.

Otherfeatures which are considered as characteristic 1 Y for theinvention are set forth in the appended claims.

member perpendicularly to the. press platen and providing less bores indirection from the center toward the edges, i.e. by disposing themfarther apart. The bores of the rib members are alsoarrangedperpendicularly to the press platen.

, It has been found that plane-parallelism of the press surfaces iseasier to obtain if the heat .or temperature bridge mernbers which aresubjected to the counter heating. I

Although the invention is illustrated and described herein as embodiedin heating platen press, it is nevertheless not intended to be limitedto the details shown, since various modifications and structural changesmay be made therein without departing from the spirit of the inventionand within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawing, in which:

FIG. 1 is a side-elevational view, partly in section, of the heatingplaten press according to the invention;

FIG. 2 is a front-elevational view of FIG. 1;

FIG. 3' is a view similar to that of FIG. 1 of another embodiment of theinvention, wherein the heating platen press has trapezoidal bridgemembers;

FIGS. 4 and 5 are enlarged side-elevational and horizontal sectionalviews, respectively, of astructural the crossbeam is provided withtwo-part rib members and with small heating plates placed around thelongitudinal center line'of the press platen.

Referring now to the drawing, and first particularly to FIGS. 1 to 3thereof, there is shown a heating platen press constructed in accordancewith the invention and having as its main parts a stationary table and amovable ram, with the stationary table being composed of a number ofindividual crossbeams 1, and the movable ram of a number of individualcrossbeams 2. The movable ram is braced, with the aid of return strokedevices, against the press cylinder piston devices formed of thepressure pistons 26, the tension columns 27 and the press cylinders 25.The individual crossbeams 1 and 2 are erected as a relatively highstructure having torsional stiffness and capable of coping with thermalexpansion, the crossbeams being assembled so that their wide side e,i.e. the outer faces of their bridge members 4, define the length of thetable and of the ram of the heating platen press. Rib memberswhich-connect the bridge members 4 are of bipartite construction and,with respect to the heating effect, are referred to as operationalheating ribs 19 and counter-heating ribs 20. Ribs 22 and 23 are locatedalong the longitudinal center line. In the effective compression surfaceregion, the press platens 3 are loosely mounted at the table and 'ram.According to the invention, bores 9 are formed not only in the pressplatens 3, but bores 11 are also provided in the rib members 20 and 23and bores and 31 in the bridge members 4.

To equalize heat expansion during the heating and cooling of the press,and also to effect minimally stressed welding of the individualcrossbeams l and 2, heat expansion openings 7 and 8 are formed about theneutral axis A-B in the bridge members 4.

In the embodiment of the heating platen press according to FIG. 3, thereare provided bridge members l6, shaped according to the invention intrapezoidal form corresponding to the curve 'of the bending moment. Forthe purpose of mounting the compression cylinder piston assembly 25, 26and 27, the bridge members 16 are again of planar form, extending fromthe longitudinal line 29 of the compressed material,

and in fact at the level i which corresponds to the bending moment atthe longitudinal line of the compressed material. To provide a preferredmeans for supplying heat to the center of the bridge members 16, bores28 are disposed therein at an inclination to the horizontal.

As shown in FIGS. 1 to 3, only the bores 11 of the counter-heating ribs20 and 23 interconnected by connecting lines 30, are included in afeasible heating and. cooling system for the table and ram.

Structural details of the individual crossbeams l for a table, are shownin FIGS.'4 to 7. The individual crossbeams according to FIGS. 4 to 5,are provided with continuous rib members 5 and 6, while the rib membersin FIGS. 6 and 7, are divided into operatively heating ribs 19 and 22and into counter-heating ribs 20 and 23, so as to effect a separation ofthe heat flow above and below the neutral axis A-B. This affords anespecially exact means for differentiatingly heating the operativelyheating rib members 19 and 22 and the counter-heating rib members 20 and23, of which the middle ribs 22 and 23 are so heated relative to theouter ribs 19 and 20, thereby to effect a thermodynamic influence upon adesired planar surface or upon a convexly bentthrough press platen. Asan aid or reinforcement of this feature, the bridge members 4 areprovided with bores 32, which run vertically in the direction of thepress platen and, between bridge members 4, small heating plates 24 withbores 18 are situated upon the press platen 3.

The small heating plates 24 are so arranged on the longitudinal centerline of the heating platen press that, although they have the bestpossible contact with the press platen 3, they have no contact with thebridge members 4. To prevent the occurrence of uncontrollabledeformations during the heating or cooling of the table and ram,heat-expansion openings 7, 8 and 15, are provided in the rib members andbridge members.

As shown in the drawing, the bridge members 4 and 16 extend to the leftand to the right hand sides across the effective compression surfaceregion and form extensions 17. Spacers 12, through an interposition orpressure-distribution plates 14, are mounted on these extensions 17 insuch a manner that, in cooperation with the extensions of the individualcrossbeams 2, they define, with the aid of spacer plates 13, the desiredpress gap. The spacer plates 13 bear upon spacer supports 12 and arethus removed from the soiled region of the compressed material plane.

Iclaim:

'1. Heatable single or multilevel platen press for the manufacture ofwood composition panels or the like, comprising a stationary basestructure and a hydraulically displaceable structure, each of saidstructures being composed of a plurality of individual bridge membersand rib members interconnecting said bridge members and formingconjointly therewith a grid-like crossbeam extending over the entirewidth of the press, said crossbearn having a relatively large moment ofinertia and being of such dimensions as to transmit the entirecompressive force of said structures; press platens loosely mounted onsaid grid at the workpieceside thereof, said rib members having fluidcirculation passages for. equalizing longitudinal thermal tensions, andsaid bridge members having fluid circulation passages for equalizingtransverse thermal tensions.

2. Heatable platen press according to claim 1, wherein said pressplaten, said bridge members and said n'b members are formed with aplurality of bores located in rows disposed one above the other in aplane.

3. Heatable platen press according to claim 2,

- wherein the bores formed in at least one of said platens,

said bridge members and said rib members extend perpendicularly to saidpress platens.

4. l-Ieatable platen press according to claim 2 having a neutral axis,and wherein small heating plates are mounted between said bridge memberson said press platens, for controlling bending. of said press platens,said small heating plates being formed with bores. 5. Heatable platenpress according to claim 4 wherein the bores of said small heatingplates are comprised of an individual controllable circulatory loop.

6. Heatable platen press according to claim 1 having a neutral axis, andwherein said rib members are divided in two and are formed ofcounter-heating rib members and operatively heating rib members forseparating the heat flow about the neutral axis.

7. l-leatable platen press according to claim 6 wherein the bores formedin said press platens, the bores formed in said bridge members belowsaid platens, the bores formed in the remainder of said bridge membersand the bores formed in said rib members form a safety circulatory loopfor operative heat- Heatable platen press according to claim 6 wherein,respectively, the bores formed in said press platens, said bridgemembers and said rib members form an individual controllable circulatoryloop.

10. l-leatable platen press, according to claim 1 wherein said bridgemembers, from the middle thereof to the marginal edges thereof areprovided with a decreasing number of bores spaced increasingly fartherapart from one another.

ll. Heatable platen press according to claim I having a neutral axis,including heat expansion openings formed in said bridge members and insaid rib members and symmetrically disposed about the neutral axis.

12. Heatable platen press according to claim I having a neutral axis,and wherein said rib members are divided in two and are formed ,ofcounter-heating rib members and operatively heating rib members forseparatingthe heat flow about the neutral axis, the bores formed in thebridge members adjacent said pressplatens being combined into acontrollable circulatory loop, and the bores formed in said pressplatens, the bores formed in the remainder of said bridge members and.the bores forrned in said rib members fonning a safety circulatory loopfor operative heating, said rib members having a temperature-severaldegrees centigrade higher, than the temperature of said bridge memberswhich are subjected to the circulatory loop a for counter-heating.

l3. Heatable platen press according to claim 12 wherein said bridgemembers are shaped according to the course of the stress by the bendingmoment, and

have a trapezoidal section. a

. l4. Heatable platen press, according to claim 13 wherein saidtrapezoidal section of said bridge members are formed with boresextending-at an angle to the horizontal.

l5. Heatable platen press according to claim 14 wherein the bores formedin said trapezoidal sections are combined into an individualcirculatoryloop.

1. Heatable single or multilevel platen press for the manufacture ofwood composition panels or the like, comprising a stationary basestructure and a hydraulically displaceable structure, each of saidstructures being composed of a plurality of individual bridge membersand rib members interconnecting said bridge members and formingconjointly therewith a grid-like crossbeam extending over the entirewidth of the press, said crossbeam having a relatively large moment ofinertia and being of such dimensions as to transmit the entirecompressive force of said structuRes; press platens loosely mounted onsaid grid at the workpiece-side thereof, said rib members having fluidcirculation passages for equalizing longitudinal thermal tensions, andsaid bridge members having fluid circulation passages for equalizingtransverse thermal tensions.
 2. Heatable platen press according to claim1, wherein said press platen, said bridge members and said rib membersare formed with a plurality of bores located in rows disposed one abovethe other in a plane.
 3. Heatable platen press according to claim 2,wherein the bores formed in at least one of said platens, said bridgemembers and said rib members extend perpendicularly to said pressplatens.
 4. Heatable platen press according to claim 2 having a neutralaxis, and wherein small heating plates are mounted between said bridgemembers on said press platens, for controlling bending of said pressplatens, said small heating plates being formed with bores.
 5. Heatableplaten press according to claim 4 wherein the bores of said smallheating plates are comprised of an individual controllable circulatoryloop.
 6. Heatable platen press according to claim 1 having a neutralaxis, and wherein said rib members are divided in two and are formed ofcounter-heating rib members and operatively heating rib members forseparating the heat flow about the neutral axis.
 7. Heatable platenpress according to claim 6 wherein the bores formed in said pressplatens, the bores formed in said bridge members below said neutral axisand the bores formed in said rib members are combined into a singlesafety circulatory loop for said operative heating while the boreslocated above said neutral axis form a circulatory loop forcounter-heating.
 8. Heatable platen press according to claim 6 whereinthe bores formed in the bridge members adjacent said press platens arecombined into a controllable circulatory loop, and the bores formed insaid press platens, the bores formed in the remainder of said bridgemembers and the bores formed in said rib members form a safetycirculatory loop for operative heating.
 9. Heatable platen pressaccording to claim 6 wherein, respectively, the bores formed in saidpress platens, said bridge members and said rib members form anindividual controllable circulatory loop.
 10. Heatable platen press,according to claim 1 wherein said bridge members, from the middlethereof to the marginal edges thereof are provided with a decreasingnumber of bores spaced increasingly farther apart from one another. 11.Heatable platen press according to claim 1 having a neutral axis,including heat expansion openings formed in said bridge members and insaid rib members and symmetrically disposed about the neutral axis. 12.Heatable platen press according to claim 1 having a neutral axis, andwherein said rib members are divided in two and are formed ofcounter-heating rib members and operatively heating rib members forseparating the heat flow about the neutral axis, the bores formed in thebridge members adjacent said press platens being combined into acontrollable circulatory loop, and the bores formed in said pressplatens, the bores formed in the remainder of said bridge members andthe bores formed in said rib members forming a safety circulatory loopfor operative heating, said rib members having a temperature severaldegrees C higher than the temperature of said bridge members which aresubjected to the circulatory loop for counter-heating.
 13. Heatableplaten press according to claim 12 wherein said bridge members areshaped according to the course of the stress by the bending moment, andhave a trapezoidal section.
 14. Heatable platen press according to claim13 wherein said trapezoidal section of said bridge members are formedwith bores extending at an angle to the horizontal.
 15. Heatable platenpress according to claim 14 wherein the bores formed in said trapezoidalsections are combined into an individual circulatory loop.